On the influence of the treatment of aerosol particles in different bin microphysical models: A comparison between two different schemes

In this paper, we compare two bin microphysical models, 1) EXMIX (EXternally MIXed) with two-dimensional distribution functions that cover the aerosol particle sizes as well as the hydrometeor sizes (120 bins from 8 nm to 7 mm) and 2) DESCAM (DEtailed SCAvenging Model) that uses separate one-dimensional functions for aerosol particles and drops. EXMIX, thus, treats the activation process in a continuous way whereas DESCAM has to manage the transfers between the aerosol particle and the droplet reservoirs thanks to threshold values such as the critical radius of activation. The analysis and comparison of the models' results show that firstly, it is necessary to introduce a temperature dependency in the activation process to stay consistent with the kinetics of aerosol particle growth and secondly, with the temperature correction proposed, DESCAM results are in good agreement with EXMIX results although the treatment of the aerosol particles is quite different in the two models. Furthermore, it is shown that DESCAM is able to reproduce quite well the main features of continental as well as maritime-type clouds, even with a low bin resolution for the microphysical grids. Finally, as DESCAM needs much less computer resources than EXMIX, it seems to be a good candidate for future use in a three dimensional framework.